WE all know what a wagging tail means. But the real sign that your dog is pleased to see you could be in its face.

A dog will raise its left brow on seeing its owner, a study has found. Seeing strangers or frightening objects, however, elicited the twitch of an ear.

The fascinating findings come from animal behaviour experts who used high-speed cameras to monitor dogs' expressions as they were shown different people.

Pet dogs, including poodles, labradors and golden retrievers, were placed in front of a set of black curtains.

They were then filmed as the curtains opened to briefly reveal either their owner or someone they'd never seen before. Small blue tags on the creatures' faces allowed the cameras to precisely track any changes in expression.

Half a second after seeing their owners, they tended to move their left eyebrow. Seeing a stranger instead led them to move their left ear. The Japanese researchers said that the choice of body part could be significant.

"Dogs' ears are prominent features used to convey emotional expression. Eyebrow movement might indicate a response whereby dogs attempted to look at their owners more intently" they said.

The researchers also examined how the dogs reacted to being shown objects they might be scared of, such as nail clippers. In this case, the action moved to the other side of the head, with the feared object resulting in movement of the right ear.

It is thought the movements on different sides of the face correspond to activity in parts of the brain that control emotion.

Movement on the right side of is normally associated with joy; dogs wag their tails more to the right on seeing their owners - but switch to the left if a strange dog appears. Though this seems to contradict the left eyebrow movement, researchers said that could be a sign of mixed emotions, with the dogs in the study happy to see their owners but upset because they were prevented from running to them.

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